1. Write "Do not come in" on the star on the paper.
2. Write "Do not come in." on the star on the paper.
(Do we have to add 'a full stop' after 'in' or not?)
No, in this construction, there should be no period or comma after 'in.'
In English grammar, a full stop (or period) is usually used to mark the end of a sentence. In the case of your sentences, whether or not to include a full stop after "in" depends on the specific context and intention of the message.
1. Write "Do not come in" on the star on the paper.
In this sentence, the absence of a full stop after "in" suggests that the instruction is simply stating not to come in, without any additional emphasis or urgency beyond that.
2. Write "Do not come in." on the star on the paper.
Including a full stop after "in" in this sentence creates a stronger emphasis on the instruction. It suggests a more forceful tone, indicating that it is important for the reader to obey the instruction immediately and without hesitation.
So, whether or not to add a full stop after "in" depends on the tone and emphasis you would like to convey in your message.